Gas cluster ion beam (GCIB) irradiation has been used for nano-scale modification of surfaces. In the co-pending, commonly held U.S. patent application Ser. No. 12/210,018, “Method and System for Modifying the Wettability Characteristics of a Surface of a Medical Device by the Application of Gas Cluster Ion Beam Technology and Medical Devices Made Thereby”, GCIB has been shown to modify the hydrophilic properties of non-biological material surfaces. GCIB processing has been well documented in the manufacturing of semiconductor devices and thin films. However, its potential uses for modifying surfaces of biological materials including tissues of the musculoskeletal system (e.g. bone, ligaments, tendons, rotator cuff, cartilage and such like), as well as for modification of other connective tissues such as epithelial tissue and endothelial tissue within major mammalian and avian organ systems are hitherto unknown. The physical modifications that GCIB processing produces on a ligament surface with respect to its capability to act as a host structure for cell attachment is hitherto unknown. It is generally known that anchorage dependent cells such as fibroblasts and osteoblasts benefit from hydrophilic surfaces to attach, grow, or differentiate well and they also prefer charged surfaces. With respect to hydrophilicity, droplet contact angle may be used as a measure of wettability, with decreasing contact angle measurements generally implying a more hydrophilic surface. Many methods have previously been employed to increase hydrophilicity or alter charge on non-biological surfaces, such as sandblasting, acid etching, plasma spraying of coatings, CO2 laser smoothing and various forms of cleaning, including mechanical, ultrasonic, plasma, and chemical cleaning techniques. Other approaches have included the addition of surfactants or the application of films or coatings having different wettability characteristics. The preparation of surfaces of biological materials by GCIB irradiation for enhanced cellular attachment either through increasing the hydrophilicity of a surface or by modifying the surface charge state or surface chemistry, or by other mechanisms has not been previously demonstrated.
Bone is often employed as a surgical grafting material to restore lost bone or to assist in fusing other bones together. Bone banks harvest, store, process, and provide bone from cadavers for use in such procedures. Conventional bone processing may include cutting or otherwise forming preformed shapes to facilitate particular uses. Examples of preformed shapes include (for examples) blocks, cylinders, and wedges for spinal cages, spacers, and other uses. Other conventional processing includes demineralization, lyophilization, disinfection, etc. Bone material may be provided (for examples) as shaped preforms, powders, suspensions in carrier liquids, or as putties. Natural bone contains bone morphogenic proteins and other bone growth factors.
Beams of energetic conventional ions, accelerated electrically charged atoms or molecules, are widely utilized to form semiconductor device junctions, to modify surfaces by sputtering, and to modify the properties of thin films. Unlike conventional ions, gas cluster ions are formed from clusters of large numbers (having a typical distribution of several hundreds to several thousands with a mean value of a few thousand) of weakly bound atoms or molecules of materials that are gaseous under conditions of standard temperature and pressure (commonly oxygen, nitrogen, or an inert gas such as argon, for example, but any condensable gas can be used to generate gas cluster ions) with each cluster ion sharing one or more electrical charges, and which are accelerated together through high voltages (on the order of from about 3 kV to about 70 kV or more) to have high total energies. After gas cluster ions have been formed and accelerated, their charge states may be altered or become altered (even neutralized), and they may fragment into smaller cluster ions and/or neutralized smaller clusters, but they tend to retain the relatively high total energies that result from having previously been accelerated through high voltages. Gas cluster ion beams have been used to process surfaces of non-biological materials for purposes of cleaning, etching, smoothing, film growth, and the like. They are well known for their smoothing effects on most solid material surfaces and have been employed for smoothing materials such as diamond, silicon, and metals. Because of the large number of atoms or molecules in each gas cluster ion, and because they are weakly bound, their effect upon striking a surface is very shallow, unlike the effect of conventional (monomer or molecular) ions. The cluster is disrupted at impact and each atom or molecule then carries only a relatively few eV of energy compared to the total energy of the accelerated cluster. Instantaneous temperatures and pressures can be very high at gas cluster ion impact sites, and a variety of surface chemistry, etching, and other effects can occur. Surface chemistry may be modified by GCIB irradiation (for example) by exposing surface bonds (thus modifying surface charge states) and/or by incorporation of reactive atoms or molecules from the gas cluster ions into the surface (by using gas cluster ions comprising reactive atoms or molecules such as oxygen, nitrogen, carbon, etc.) However, these effects are very superficial, extending, at most, some tens of Angstroms beneath the impact site and accordingly there is no significant damage to any material located deeper below the superficial surface impact site.
It is therefore an object of this invention to provide methods for increasing the wettability and/or altering the chemistry or charge state and/or modifying other physical characteristics of a surface of a biological material such as bone by the application of gas cluster ion beam technology in the form of a gas cluster ion beam irradiation and/or accelerated neutral beam irradiation.
It is a further object of this invention to provide methods for preparing a surface of a biological material such as bone for attachment, proliferation, migration, etc. of new cellular growth, by the application of gas cluster ion beam technology in the form of a gas cluster ion beam irradiation and/or accelerated neutral beam irradiation, and optionally, for the stimulation of the new cells to differentiate into tissue such as bone, fibrous connective tissue, epithelium, endothelium or the like.
Another object of this invention is to provide methods for increasing the wettability of a portion of a surface of a biological material and/or for preparing a surface of the biological material for attachment, proliferation, migration, etc. of new cellular growth, in a controlled pattern, by the application of gas cluster ion beam technology in the form of a gas cluster ion beam irradiation and/or accelerated neutral beam irradiation.
A still further object of this invention is to provide a surgically implantable biological material that has a surface or surface portion with increased hydrophilicity and/or that has a surface with an enhanced capability to act as a host for new cellular attachment, growth, and differentiation, by the application of gas cluster ion beam technology in the form of a gas cluster ion beam irradiation and/or accelerated neutral beam irradiation, and optionally, for the stimulation of the new cells to differentiate into tissue such as bone, fibrous connective tissue, epithelium, endothelium or the like.
Another object of this invention is to provide a bone material for surgical implantation and/or graft, which bone material has a modified rate of release of natural growth factors therefrom, to improve post-implant integration.
It is a further object of this invention to provide methods for treating bone to enhance its suitability for surgical implantation by increasing biocompatibility and/or providing for delayed or enhanced release of growth factors and to provide materials treated thereby.